Air disinfection method and a device for implementation thereof

ABSTRACT

A device and methods for air disinfection of microorganisms and biological agents by the method of their inactivation by electrostatic fields and filtering by the method of electrostatic precipitation is disclosed. The method comprises the steps of: creating a flow (A) of air to be disinfected; subjecting said flow to constant with electrostatic fields alternating in direction of intensity vector, said electrostatic fields being sequentially arranged along the flow, and created by transversely spaced air permeable electrodes ( 1 ); and filtering the treated flow with an electrostatic filter. Electrostatic field concentrators in the form of projections ( 3 ) are located on the surface of the electrodes ( 1 ), in particular nanoscale projections. This provides a fast, effective, and reliable cleaning of air from any kind of microorganisms and viruses, as well as the aerosol particles having size of 0.08 μm.

CROSS REFERENCE APPLICATIONS

This application is a Divisional of U.S. patent application Ser. No.:14/815,142 filed Jul. 31, 2015, the content of which is incorporatedherein by reference.

TECHNICAL FIELD

The invention relates to the field of disinfection and purification ofair of microorganisms and aerosols, namely to methods of airdisinfection of microorganisms and biological agents by their permanentinactivation by impact of electrostatic fields and filtration byelectrostatic precipitation.

The invention can be used for disinfection and purification of air incombined extract-and-input ventilation systems of <<biologically clean>>areas in medicine, pharmaceutical, microbiological, and food industryand other areas where it is required to ensure infectious andsanitary-epidemiological safety of air. Furthermore, the invention canbe used for disinfection of air in transport means including passengertransportation by road and rail, air transportation, space manned flyingmachines, waterborne and underwater means, etc., as well in personalprotective equipment (bioprotective and of anti-aerosol masks, etc.), inautonomous recycling facilities and other equipment.

BACKGROUND ART

A device for sterilizing gas and fine filtration is disclosed in RU2026751. Said device realizes the method of inactivation ofmicroorganisms comprising inactivation of microorganisms in the airflow, wherein they first are charged by ions of the same or differentsigns, and then said microorganisms are retained on the electrostaticfilter, where they eventually are inactivated. Two ionizers of differentpolarities can of used in the devices for enhancing the sterilizationeffect.

However, in such devices the inactivation of microorganisms is carriedout only after their retention in the electrostatic filter, which isundesirable as during operation constant accumulation of livingmicroorganisms occurs, and the risk of multiple ejection from the devicein the environment increases.

Furthermore, for inactivation of microorganisms, it is necessary tocreate high concentration of ions within each said device, which isalways accompanied by emission of a significant amount of ozone andnitrogen oxides. Discharge of said gases in the air in highconcentrations is dangerous for humans and animals. At the same time,the effectiveness of the inactivation depends on the concentration ofions and ozone within the apparatus, which limits the reliability ofoperation of such apparatuses.

An apparatus for inactivation and fine filtration of viruses andmicroorganisms in the air stream is disclosed in RU 2344882. Saidapparatus comprises a high voltage power source; a sequentially arrangeddownstream the air flow means for preliminary treating the air flow, themeans being formed of oppositely charged conductive filter elements,between which a dielectric plate of a highly porous permeable materialis located; a two-section inactivation chamber, each section comprisingcoaxially arranged a needle corona electrode and a cylindricalnon-corona electrode, each of which is electrically connected to acorresponding conductive filter plate, and a precipitator made ofparallel oppositely charged plates of highly porous permeable conductivematerial, between which plates of permeable highly porous dielectricplates are placed. At least a first downstream conductive filter elementof the preliminary treatment means is configured as a cylindricalelectrode with a base in the form of a conductive plate made of a porouspermeable conductive material adjacent to a plate of a permeable highlyporous dielectric material and a plate of highly porous conductivematerial arranged at a distance from the free end of the cylindricalelectrode, said plate being adjacent to the electrically connectedneedle electrode arranged coaxially to the cylindrical electrode andhaving its point directed towards the dielectric plate, wherein thecylindrical and needle electrodes are connected to opposite poles of thepower supply. In the apparatus, porous permeable electrodes having athree-dimensional structure are used, such as open-cell structure of thebulk material (foamed metal).

During operations of the apparatus, a required concentration of ions ofcorresponding signs is obtained. In the preliminary treatment means,bioaerosols are charged, and the electric fields of different intensityand gradient act on them. <<Cold plasma>> makes an impact onmicroorganisms at the points of the needle corona electrodes.

In said apparatus first rough filtering of air from large particles isperformed. Then, microorganisms and viruses are charged by the ions ofone sign, then by the ions of the opposite sign.

After the preliminary treatment means, the air flow enters thetwo-section chamber inactivation equipped with two single-ended or thedischarge electrodes of different polarities.

In a two-section inactivation chamber multiple recharging of bioaerosoltakes place under the action of ions, due to electrical contact with theelectrodes of different polarity and the surface of the polarizeddielectric filter material. After passing through the inactivationchamber, existing microorganisms and viruses in the air flow will be inthe inactivated state.

After passing the inactivation cameras, the particles get sufficient forprecipitation charge, and they are retained in the electrostaticprecipitator.

The prior art apparatus and the method implemented by said apparatusallow overcoming the disadvantages inherent in the described aboveapparatus according to RC 2026751. However, the process of inactivationof microorganisms and viruses requires simultaneous provision of manyconditions: simultaneously creating a high concentration of ions of thesame or different polarity, ozone, intensity of electrostatic fields,and polarization of the dielectric. Simultaneous provision of saidconditions and ensuring high efficiency of the inactivation ofmicroorganisms in the apparatus is technically difficult because each ofthese factors affects the result of the processing. The efficiency ofinactivation of microorganisms in such apparatus depends on theconcentration of ions and ozone within the apparatus, dielectricproperties, intensity of the electric fields between the electrodes, andother characteristics. It greatly affects the reliability of theapparatus. Furthermore, for decomposition of ozone in such apparatusrequires use of a catalysts, which require constant monitoring of theirperformance, thereby limiting the safe use of this apparatus in premiseswith people, and requires additional measurements to ensure operationsafety.

The main purpose of the invention is to improve the efficiency of airdisinfection by using for rapid inactivation of a microorganism cellelectroporation in electrostatic fields followed by filtration ofinactivated microorganisms and particulate matter in an electrostaticprecipitator.

Further objects of the present invention are to reduce the discharge ofozone and other harmful substances in the process of air disinfection,and to improve reliability of the apparatus.

SUMMARY OF INVENTION

Said problems are solved by the claimed air disinfection method, whichincludes the steps of: providing a air flow to be disinfected;subjecting said flow to the action of electrostatic fields beingarranged successively along the flow, said fields alternating in thedirection of the intensity vector are created by transversely positionedelectrodes permeable to air; and filtering the treated air flow by anelectrostatic filter. According to the invention, there areelectrostatic field concentrators in the form of projections with thebase diameter not exceeding 30 μm are formed on the surface of theelectrodes, and the intensity of each of the alternating electrostaticfields between the corresponding electrodes is selected in accordancewith the condition of electroporation of microorganism cells or theirinactivation.

As a result of exposure of a microorganism cell to electrostatic fieldsdirected in opposite directions and their high local intensity near theelectric field concentrators the magnitudes and polarity of electricpotentials on the surface and inside the cell repeatedly changes,whereby there is a change in cell structure, its mechanical andelectrical properties, electroporation of cells of microorganisms(formation of pores in the cell membrane) and the subsequentdisintegration (distraction) of the structure.

Preferably, the intensity of each of the alternating electrostaticfields between the electrodes is at least 2 kV/cm.

It is desirable to have nanoscaled protrusions with a base diameter ofless than 100 nm .

The air flow permeable electrodes are in the shape of plates of porouselectrically conductive material or bulk porous fibrous structures.

Preferably, highly porous dielectric plates are arranged between theelectrodes. Nanosized projections can also be formed on the surfaces ofsaid plates.

The air flow rate is selected so that the exposure time of each of thepermanent alternating electric fields on the particles moving in the airflow to be disinfected is not less than 0.05 seconds.

Preferably, several zones with a high concentration of ions areadditionally arranged along the air flow.

The presence of zones with a high concentration of the ions allowscharging the aerosol particles by positive and/or negative ions, whichenhances the effect of precipitation of these particles.

The zones with a high concentration of ions are preferably formed byperforming a corona discharge.

In a part of these zones, there is high concentration of ions of tiepolarity, and in the rest zones, the ions are of the other polarity.

Furthermore, the zones with high concentration of ions can be arrangedalong the air flow before the impact on the air flow by electrostaticfields and/or between the electrodes creating the fields.

The above problems are also solved by an apparatus for disinfecting theair flow comprising the sequentially arranged along the air flowelectrodes in the form of permeable for air flow conductive platesarranged across the flow, and a high voltage power source connected tothe electrodes so that electrodes have alternating polarity. Accordingto the invention, the electrodes are on the surface of the electricfield concentrator in the form of projections, the base diameter notexceeding 30 μm.

The concentrators of electrostatic field on the electrodes provide theappearance of local zones of high intensity, and the alternation ofthese local zones, the zones of low intensity and the zones withoutintensity of the electrostatic fields when the direction and magnitudeof the intensity of these fields change, leads to rapid electroporationof microorganism cells and disintegration of their structure.

Preferably, the projections are nanosized with a base diameter of notmore than 100 nm.

Conductive plates permeable for the air flow and made of a porouselectrically conductive material or bulk porous fibrous conductivestructures can be additionally provided.

Highly porous dielectric plates also having nanosized projections ontheir surfaces can be additionally arranged between the electrodes.

At least one zone with a high concentration of ions can be formedbetween the electrodes.

If several zones of a high concentration of ions are formed between theelectrodes, the ions of said zones of high concentration are of the samepolarity, and the ions of in other zones are of the other polarity.

Preferably, the zones with a higher concentration of ions of the samepolarity alternate with zones of high concentration of ions of theopposite polarity.

In addition, before the first electrode downstream the air flow, atleast one zone of a high concentration of ions is formed. If there areseveral such zones, it is preferable that the ions in these zones are ofthe same polarity.

All the above zones of high concentration of ions can be formed byperformed as a needle corona electrode arranged coaxially with anon-corona cylindrical electrode.

Preferably, at least one zone of a higher concentration of ions islimited at the inlet by a highly porous permeable electrode of polaritycoinciding with the polarity of the nearest electrode, wherein at theoutlet said zone can also be limited by a highly porous permeableelectrode of polarity coinciding with the polarity of the nearestelectrode.

BRIEF DESCRIPTION OF DRAWINGS

The foregoing and other features and aspects of the invention will bebest understood with reference to the following description of certainexemplary embodiments of the invention, when read in conjunction withthe accompanying drawings, wherein:

FIG. 1 is a cross-sectional schematic view of an apparatus fordisinfecting air according to the invention;

FIG. 2 is the same view, but with a highly porous dielectric platesbetween the electrodes;

FIG. 3 is the same view as in FIG. 2 but with zones of a higherconcentration of ions formed between the electrodes:

FIG. 4 is same view as in FIG. 3, but with the zone of a highconcentration of ions formed before the first electrode downstream ofthe air flow;

FIG. 5 is the same view as in FIG. 4, but with the highly porouspermeable electrode at the inlet to the zone with a high concentrationof ions formed before the first electrode downstream of the air flow;

FIG. 6 is the same view as in FIG. 5, but with a highly porous permeableelectrode at the outlet of the zone with a high concentration of ionsformed before the first electrode downstream the air flow;

FIG. 7 is a diagram of changes of the electrostatic field intensity nearthe nanoscaled projections on an electrode;

FIG. 8 is a cross-sectional view of an embodiment of a needle coronaelectrode.

Implementation of the method according to the invention is illustratedby the embodiment of the apparatus schematically shown in the Figures.

FIG. 1 shows the simplest embodiment of an apparatus implementing themethod according to the invention.

BEST MODE FOR CARRYING OUT THE INVENTION

The apparatus comprises electrodes 1 arranged sequentially along the airflow A of 1 in the form of permeable to air flow conductive plateslocated across the flow, and a high voltage power source 2 connected tothe electrodes 1 so that the electrodes 1 have alternating polarity. Theplates of electrodes 1 can be made of various materials: permeable foammetals, porous electrically conductive powder materials, bulk fibrousporous structures, and the like. It is only required to have in theplates of such electrodes an average pore size of not more than 6 mm. Onthe surface of the electrodes, there are electrostatic fieldconcentrators in the form of projections 3 (FIG. 7), with a basediameter not exceeding 30 μm. Preferably, the projections 3 arenanosized with a base diameter of not more than 100 nm. The nanosizedprojections 3 on the surface of the electrode 1 can be obtained, e.g.,by powder metallurgy techniques. The power supply 2 is selected on theconditions of creating electrostatic field of intensity not less than 2kV/cm between the adjacent electrodes 1. In this case, near thenanosized protrusions 3, the diameter of which does not exceed the abovevalue, the intensity of the electrostatic field reaches 100 kV/cm ormore. As studies have shown, that causes an electrical breakdown of themicrobial cell membrane. For creating the required potential differencebetween the electrodes and the reliability and stability of theapparatus operations, the high voltage power supply must ensure thestabilization of voltage or current.

In operation of the apparatus, an air flow containing microorganisms andaerosol particles passes through the highly porous electrode 1 having onits surface electrostatic field concentrators in the form of protrusions3. Near the surface of the electrodes, a local high intensityelectrostatic field exceeding 100 kV/cm is created due to theprojections 3.

The passage of microorganisms through electrostatic fields repeatedlyalternating in direction and magnitude leads to multiple changes in themagnitude and polarity of the electric potentials on the surface andwithin the cell resulting in changes of cell structure and itselectrical and mechanical properties. As a result of repeateddepolarization of the cell, in its membrane pores (electroporation) areformed, and its structure disintegrates (is destructed), Inactivation ofmicroorganisms by disrupting their structure eliminates any possibilityof adaptations to such impacts, mutations or restoration (<<revival>>),i.e., the inactivation is irreversible. The number of electrodes 1 withprojections 3 and the number of direction changes of the electrostaticfields is determined based on the processing air flow rate and theparameters of the processed air. The time required to inactivate allmicroorganism species can be about 0.5 seconds. Inactivatedmicroorganisms and particulate matter are trapped by the electrostaticfilter (not shown). The highly porous dielectric plates 4 can bearranged between the electrodes (FIG. 2) for preventing an electricalbreakdown between the electrodes 1 when changing the air or gaseousmedium (moisture, dust, temperature, etc.), equalizing the air flow ratein the cross section of the apparatus, and retaining aerosol particleson the surface.

The device can be equipped with one or more ionization cameras 5 (FIG.3) for creating zones with a high concentration of ions to improve theefficiency of the apparatus in high humidity, The electrical parametersof the ionization chambers are chosen such that emission of ozone andnitrogen oxides do not exceed their normalized values. The ionizationchamber 5 can be formed as coaxially arranged a needle corona electrode6 and a cylindrical non-corona electrode 7, In particular, the coronaelectrode is a needle, such as a wire 8 (FIG. 8) mounted in a metal pipe9 coaxially thereto and projecting therefrom on an amount sufficient toproduce an electrical corona. FIG. 3 shows three ionization chambers 5,wherein in the first and he last chambers downstream the flow the coronaelectrode is connected to one pole of the power supply 2, and the middlechamber is connected to the other pole, so that the zone with a higherconcentration of ions of one plate alternate with the zones of increasedconcentration of ions of the opposite polarity. However, if there areseveral ionization chambers in the apparatus, these chambers may belocated arbitrarily, without requiring interleaving zones with a highconcentration of ions of opposite polarity (not shown). For efficientfiltration without increasing emission of ozone, the ionizationchambers, for example, can generate ions of the same polarity.

For creating the best conditions for operations of the apparatuscomprising the ionization chambers, the power source is configured sothat the electrodes 1 are supplied with a constant in value voltage, andthe ionization chambers are supplied with stabilized current.

For increasing the intensity of exposure to the aerosol particles andimproving the stability of the apparatus in high humidity and dust inthe air, is desirable to pre-charge these particles with positive and/ornegative ions. For this purpose, at least one zone with a highconcentration of ions (FIG. 4) is formed before the first downstreamelectrode 1 as an ionization chamber 10 similar to any of the ionizationchambers 5 located between the electrodes 1.

The ionization chamber 10 can be limited at the input by a highly porouspermeable electrode 11 (FIG. 5), whose polarity coincides with thepolarity of the nearest electrode 1. A highly porous permeable electrode12 (FIG. 6) can also be disposed at the output of the ionization chamber10, the polarity of which coincides with the polarity of the nearestelectrode 1.

Limitation of the ionization chamber 10 at the inlet and/or outlet withthe highly porous permeable electrodes 11 and/or 12 improves theconditions of charging aerosols inside the chamber and facilitates theimplementation of multiple recharging the bioaerosol when passingthrough the apparatus.

For increasing the amount of the preliminary charge of aerosol particlesby positive and/or negative ions of the ionization chambers 10 disposedin front of the first downstream electrode, there can be a few suchchambers (not shown).

Monitoring the effectiveness of air disinfection can be carried out bymonitoring the electrical parameters of the apparatus elements(currents, voltages, etc.).

The use of the invention provides a fast, effective, and reliablecleaning of air from of any kind of microorganisms and viruses, as wellas the aerosol particles having size of 0.08 μm or more. At the sametime, the invention also provides hygienic safety due to inactivation ofmicroorganisms before the filtration step, and because of the absence ofdangerous concentrations of ozone and other harmful substances.

If necessary, the purification of air from harmful and unpleasantsmelling substances, one or more plates of highly porous electrodes orthe plates of highly porous dielectric can have adsorption-catalyticcoating.

If it is required to increase the efficiency of the filtration ofaerosol particles, additional filter material or a high efficiencyfilter can be installed between the electrodes of the apparatus.

1-11. (cancelled)
 12. An apparatus for disinfecting air flow, saidapparatus comprising electrodes in the form of air permeable conductiveplates arranged successively downstream across the flow, and a highvoltage power source connected to the electrodes so that the electrodeshave alternating polarity, characterized in that the electrodes have ontheir surfaces concentrators of the electrostatic field in the form ofprojections with the base diameter not exceeding 30 μm.
 13. Theapparatus according to claim 12, characterized in that the nanosizedprojections have a base diameter of not more than 100 nm.
 14. Theapparatus according to claim 12, characterized in that the air permeableconductive plates are made of a conductive porous material or a bulkconductive fibrous porous structures.
 15. The apparatus according toclaim 12, characterized in that additionally air permeable highly porousdielectric plates are arranged between the electrodes.
 16. The apparatusaccording to claim 15, characterized in that the highly porousdielectric plates have on their surfaces nanosized projections.
 17. Theapparatus according to claim 12, characterized in that at least one zonewith a high concentration of ions is arranged between the electrodes.18. The apparatus according to claim 17, characterized in that theelectrodes are formed with several zones of increased ion concentration,wherein a portion of said zones of increased concentration of ions haveone polarity, and the other zones have the opposite polarity.
 19. Theapparatus according to claim 18, characterized in that the zones with ahigh concentration of ions of one polarity alternate with the zones ofhigh concentration of ions of the opposite polarity.
 20. The apparatusaccording to claim 12, characterized in that before the first electrodedownstream the air flow at least one zone with a high concentration ofions formed.
 21. The apparatus according to claim 20, characterized inthat, before the first electrode downstream the air flow, several zonesof high concentration of ions of one polarity are formed.
 22. Theapparatus according to claim 17, characterized in that the zone with ahigh concentration of ions is formed as coaxial needle corona andcylindrical non-corona electrodes.
 23. The apparatus according to claim20, characterized in that the zone with a high concentration of ions isformed as coaxial needle corona and cylindrical non-corona electrodes.24. The apparatus according to claim 22, characterized in that at leastone zone of a high concentration of ions limited at the inlet by highlyporous permeable electrode of polarity coinciding with the polarity ofthe nearest electrode.
 25. The apparatus according to claim 24,characterized in that at least one one of a high concentration of ionsis limited at the outlet by highly porous permeable electrode ofpolarity coinciding with the polarity of the nearest electrode.